The present invention relates to tampon applicators and in particular to biodegradable tampon applicators formed of poly 3-hydroxybutyric acid (PHB).
Tampon applicators are not supposed to be disposed of via the sanitary and sewage systems. However, it is often the case that they are. A popular material for tampon applicators is polyethylene which is a non-degradable plastic. Thus disposal of polyethylene tampon applicators will cause accumulation and clogging in sanitary and sewage systems, in particular in septic tank systems. Furthermore such polyethylene applicators are not degraded in sewage treatment plants and are often passed out into the environment to be washed up on the shores of rivers, lakes and oceans. Thus it is a problem of the art to provide tampon applicators which overcome or ameliorate the sanitary and environmental disadvantages of those applicators commonly used.
U.S. Pat. No. 2518486 suggests the use of tampon applicators made of water-soluble polyvinyl alcohol. However, such applicators have been found to become sticky on contact with damp surfaces and to become relatively unstable in humid conditions. U.S. Pat. No. 3882869 is also directed to the problem of disposal of tampon applicators and proposes the use of a water soluble polymer compounded with filler material such as clay, talc, wood, flour or fibres. Such applicators are said to have a lower tendency to adhere to moist human tissue. Nevertheless, they are still formed of water-soluble polyvinyl alcohol with the inherent disadvantages thereof. U.S. Pat. No. 3954104 discloses a thermoplastic, water-dispersible, biodegradable composition which can for example be used to make a tampon applicator. The composition comprises hydroxycellulose which is biodegradable and water-soluble and starch as a biodegradable filler. Again these tampon applicators contain a water soluble material.
U.S. Pat. No. 4372311 seeks to solve this problem by providing disposable articles made from a water-soluble polymer, a surface of which articles being coated with a degradable water-insoluble polymer. The disposable articles include diapers, tampons, tampon applicators, sanitary napkins, bed liners and bandages. It is acknowledged that the utility of articles made from a water-soluble polymer is limited because even casual contact with moisture will cause the surface to become tacky or slippery thus interfering with the proper function of the article. Thus U.S. Pat. No. 4372311 proposes coating the water-soluble polymer with a water-insoluble polymer for protection. Poly .beta.-hydroxybutyrate is one of a number of degradable water-insoluble polymers which, it is stated, may be used as a coating. The coating may be applied for example by dipping, spraying or brushing.
Further attempts to solve the problem of providing disposable tampon applicators that are stable on storage have involved the study of paper or cardboard applicators. These are generally unsatisfactory because of poor durability in handling, packaging and use; they have a low crush resistance, poor bending strength and relatively poor frictional characteristics. Furthermore, they absorb relatively high quantities of moisture thereby enhancing the lack of durability.